JP2010194731A - Method for producing radial tire for aircrafts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a radial tire for aircrafts which makes it possible to improve durability. <P>SOLUTION: In the method for producing the radial tire for aircrafts having a carcass layer 4 including turnup plies 4A of a plurality of layers and turndown plies 4B of a plurality of layers which are wound up around a bead core 5, the turnup ply 4A is made cylindrical to mold a turnup ply cylindrical body 14A, the turndown ply 4B is made cylindrical to mold a turndown ply cylindrical body 14B having a periphery length equal to/or below the inner circumference length of the turnup ply cylindrical body 14A, the turnup ply cylindrical body 14A is arranged on the periphery of a tire molding drum 13, both ends of the turnup ply 4A are wound up around the bead core 5, the turndown ply cylindrical body 14B is expanded and arranged on the periphery of the turnup ply cylindrical body 14A, both ends of the turndown ply 4B are folded to the inside in the radial direction of the bead core 5 to expand the carcass layer 4, so that the tire is molded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for manufacturing a radial tire for an aircraft having a carcass layer composed of a turn-up ply and a turn-down ply, and more specifically, a radial tire for an aircraft capable of improving durability by devising a molding process. It relates to the manufacturing method.

  Bias tires are the mainstream for aircraft tires, but radial tires have also become popular in recent years. As such an aircraft radial tire, for example, a bead core embedded in each of a pair of left and right bead portions, and a plurality of turns wound around each bead core and wound from the inside of the tire to the outside. A carcass layer comprising a plurality of turn-down plies positioned outside the turn nap ply and the bead core radially inward from the turn nap ply, and a belt disposed on the outer periphery of the carcass layer in the tread portion The thing provided with the layer is proposed (for example, refer patent document 1).

  When manufacturing a radial tire for an aircraft configured as described above, a plurality of layers of turn-up plies are wound around a tire-forming drum, and both ends of the turn-up plies are wound up around the bead cores. A plurality of turn-down plies are wound around the ply, and both ends of the turn-down ply are folded inward in the radial direction of the bead core to form a primary green tire. Thereafter, the carcass layer composed of the turn-up ply and the turn-down ply is expanded while the mutual interval between the bead cores is reduced, and an annular belt layer is bonded to the outer periphery of the carcass layer, and the bead core, the carcass layer, and the belt layer are included. A secondary green tire is formed and the secondary green tire is vulcanized in a mold.

  In the aircraft radial tire manufacturing method described above, when the circumference of the carcass layer on the tire molding drum is set to be small (for example, close to the inner circumference of the bead core), in the molding process, the tread portion and the sidewall When the carcass layer is greatly stretched in the tire circumferential direction at the portion, the carcass cord driving density in the tread portion and the sidewall portion is lowered in the vulcanized tire. Therefore, if the circumference of the carcass layer on the tire molding drum is set to be small, the tire rigidity is lowered, which is disadvantageous in terms of durability.

  On the other hand, in the aircraft radial tire manufacturing method described above, when the circumference of the carcass layer on the tire molding drum is set to be large, the driving density of the carcass cords in the tread portion and the sidewall portion in the vulcanized tire is Since it becomes high, it is possible to increase tire rigidity. However, if the circumferential length of the carcass layer on the tire molding drum is set to be large, both ends of the carcass layer are narrowed down in the molding process, so that the carcass layer has a minimum circumferential length in the vicinity of the bead base portion. It becomes easy to produce wrinkles in the layer. In particular, the bead base portion, which is the contact portion between the rim and the tire, is always loaded when the tire is mounted on the rim, so if there are wrinkles in the carcass layer in the vicinity of such a bead base portion, It is easy for a failure to occur. Therefore, even if the tire rigidity increases, the durability of the bead portion deteriorates, and the effect of increasing the durability of the entire tire cannot be obtained.

JP 2003-320809 A

  The objective of this invention is providing the manufacturing method of the radial tire for aircraft which enabled the improvement of durability by devising a shaping | molding process.

  In order to achieve the above object, a method for manufacturing a radial tire for aircraft according to the present invention includes a bead core embedded in each of a pair of left and right bead portions, and a bead core mounted between the bead portions so as to surround each bead core from the inside to the outside of the tire. A plurality of turn-up plies wound up and a carcass layer located outside the turn-up plies and folded into the radial inner side of the bead core from the tire outer side, and the carcass layer in the tread portion. In a method of manufacturing a radial tire for an aircraft having a belt layer disposed on the outer periphery of a carcass layer, a turn-up ply cylinder is formed by forming a plurality of turn-up plies into a cylindrical shape, and then turning down the layers The ply is cylindrical and has an outer circumferential length equal to or less than the inner circumferential length of the turn-up ply cylinder. Forming a turn-down ply cylinder, placing the turn-up ply cylinder on the outer periphery of a tire molding drum, winding both ends of the turn-up ply around a bead core, and The turn-up ply and the turn-up ply are arranged on the outer periphery of the turn-up ply cylinder, folded at both ends of the turn-down ply inward in the radial direction of the bead core, and the bead core is reduced in mutual spacing. A carcass layer composed of a down ply is inflated and an annular belt layer is bonded onto the outer periphery of the carcass layer, an unvulcanized tire including the bead core, the carcass layer and the belt layer is formed, and the tire is placed in the mold. It is characterized by being vulcanized with.

  As a result of intensive research on radial tires for aircraft, the present inventor has found the following points and has reached the present invention. That is, in an aircraft radial tire having a carcass layer composed of a turn-up ply and a turn-down ply, the turn-down ply is folded inward in the radial direction of the bead core, but the folded portion of the outermost layer is the largest in the lower region of the bead core. It will be arranged inside the direction. Therefore, the outermost layer of the turndown ply is most prone to wrinkles in the tire molding process. On the other hand, when the functions of the turn-up ply and the turn-down ply as rigid members are compared, the turn-down ply does not involve the bead core, so the contribution to the rigidity is small. In other words, if sufficient rigidity is ensured based on the turn-up ply around which the bead core is wound, even if the rigidity based on the turn-down ply is reduced, the effect is negligible.

  Therefore, in the present invention, the turn-up ply cylinder and the turn-down ply cylinder are formed in separate processes, and the outer peripheral length of the turn-down ply cylinder is set equal to or less than the inner peripheral length of the turn-up ply cylinder. By doing so, wrinkles are prevented from occurring in the turndown ply in the vicinity of the bead base portion while minimizing the decrease in the rigidity of the carcass layer, and the durability of the entire tire including the bead portion is improved.

  In the present invention, the ratio of the outer peripheral length of the turn-down ply cylinder to the inner peripheral length of the turn-up ply cylinder is preferably set in the range of 0.95 to 1.0. The ratio of the outer peripheral length of the turndown ply cylinder to the inner peripheral length of the bead core is preferably set in the range of 1.06 to 1.18. Furthermore, the ratio of the inner peripheral length of the turn-up ply cylinder to the inner peripheral length of the bead core is preferably set in the range of 1.08 to 1.12. Thereby, it is possible to effectively improve the durability of the radial tire for aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a meridian half cross-sectional view showing an aircraft radial tire according to an embodiment of the present invention. The manufacturing method of the radial tire for aircraft which consists of embodiment of this invention is shown, (a)-(e) is sectional drawing which shows each process in a tire formation process roughly.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an aircraft radial tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. As shown in FIG. 1, a carcass layer 4 composed of a plurality of aligned carcass cords is mounted between a pair of bead portions 3 and 3. The angle of the carcass cord with respect to the tire circumferential direction is set in the range of 85 ° to 90 °. As the carcass cord, an organic fiber cord such as nylon or polyester can be used. The carcass layer 4 includes a plurality of turn-up plies 4A and a plurality of turn-down plies 4B. The turn-up ply 4A is wound up around the bead core 5 embedded in the bead portion 3 from the inside of the tire to the outside. On the other hand, the turn-down ply 4B is located outside the turn-up ply 4A and is folded inwardly of the bead core 5 from the outside of the tire. In this type of aircraft radial tire, it is desirable that the turn-up ply 4A has 3 to 5 layers and the turn-down ply 4B has 2 to 3 layers.

  Further, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a belt layer 6 including a plurality of layers of belt plies 6A including a plurality of aligned belt cords is disposed. The angle of the belt cord with respect to the tire circumferential direction is set in a range of 0 ° to 17 °. A steel cord is preferably used as the belt cord, but a highly elastic organic fiber cord such as aramid may be used.

  2A to 2E show a method for manufacturing a radial aircraft tire according to an embodiment of the present invention. When manufacturing the above-described aircraft radial tire, as shown in FIG. 2A, while the turn-up ply cylindrical body 14A is formed by sequentially winding a plurality of turn-up plies 4A around the band forming drum 11. As shown in FIG. 2 (b), a plurality of turn-down plies 4B are sequentially wound around the band forming drum 12 so as to have an outer peripheral length equal to or less than the inner peripheral length of the turn-up ply cylindrical body 14A. The down-ply cylindrical body 14B is formed. That is, when the inner diameter of the turn-up ply cylinder 14A is Da and the outer diameter of the turn-down ply cylinder 14B is Db, the relationship of Db ≦ Da is satisfied. Here, one turn-up ply cylinder may be formed from the turn-up ply 4A used for one tire, but when the number of turn-up plies 4A is large, the turn-up ply 4A is turned into a plurality of turns. You may divide into a nap ply cylinder.

  Next, as shown in FIG. 2 (c), the turn-up ply cylinder 14 </ b> A is coaxially disposed on the outer periphery of the tire forming drum 13, and both ends of the turn-up ply 4 </ b> A are wound up around the bead core 5. . Next, as shown in FIG. 2 (d), the turn-down ply cylinder 14B is expanded in diameter and coaxially disposed on the outer periphery of the turn-up ply cylinder 14A. Fold inward in the radial direction. Thus, a primary green tire including the bead core 5 and the carcass layer 4 is formed. Although a specific description is omitted here, the primary green tire is assumed to include necessary tire components such as a bead filler, a rim cushion rubber, and a side rubber.

  Next, as shown in FIG. 2 (e), the primary green tire is transferred to a secondary molding apparatus having a pair of clamp rings 15, and the turn-up ply 4A and the turn-down ply are reduced while the mutual interval between the bead cores 5 is reduced. The carcass layer 4 made of 4B is expanded by an internal pressure load, and a belt layer 6 made of a plurality of layers of belt plies 6A formed in a ring shape on the outer periphery of the carcass layer 4 is bonded together. Thereby, a secondary green tire including the bead core 5, the carcass layer 4, and the belt layer 6 is formed. Although a specific description is omitted here, it is assumed that the secondary green tire includes necessary tire components such as tread rubber.

  Thereafter, the secondary green tire molded as described above is put into a mold and vulcanized in the mold, whereby a desired radial tire for an aircraft can be obtained.

  In the aircraft radial tire manufacturing method described above, the inner peripheral length of the turn-up ply cylinder 14A made up of the turn-up ply 4A is set large so that the tread portion 1 and the sidewall portion 2 in the vulcanized tire Since the driving density of the carcass cord is increased, sufficient tire rigidity can be ensured. Here, the ratio of the inner peripheral length of the turn-up ply cylindrical body 14A to the inner peripheral length of the bead core 5 is preferably set in the range of 1.08 to 1.12. That is, when the inner diameter of the bead core 5 is Dc, the relationship of 1.08 × Dc ≦ Da ≦ 1.12 × Dc is satisfied. If this ratio is less than 1.08, the tire stiffness decreases, and conversely if it exceeds 1.12, wrinkles are likely to occur in the turn-up ply 4A.

  On the other hand, the wrinkles generated in the turndown ply 4B can be reduced by setting the outer peripheral length of the turndown ply cylindrical body 14B composed of the turndown ply 4B folded inward in the radial direction of the bead core 5. Moreover, since the turndown ply 4B does not involve the bead core 5 and contributes little to the rigidity, the carcass cord of the turndown ply 4B in the vulcanized tire can be set by setting the outer peripheral length of the turndown ply cylinder 14B small. Even if the driving density of the tire becomes low, a decrease in tire rigidity can be minimized. As a result, the tire rigidity based on the carcass layer 4 is sufficiently secured to sufficiently secure the durability as a pressure vessel, and at the same time, wrinkles generated in the carcass layer at the bead portion are reduced to improve the durability of the bead portion. be able to.

  Here, the ratio of the outer peripheral length of the turn-down ply cylindrical body 14B to the inner peripheral length of the turn-up ply cylindrical body 14A is preferably set in the range of 0.95 to 1.0. That is, the relationship of 0.95 × Da ≦ Db ≦ 1.0 × Da is satisfied. If this ratio is less than 0.95, the tire stiffness decreases and it becomes difficult to cover the turn-down ply cylinder 14B with the turn-up ply cylinder 14A. Prone to wrinkles.

  The ratio of the outer peripheral length of the turndown ply cylinder 14B to the inner peripheral length of the bead core 5 is preferably set in the range of 1.06 to 1.18. That is, the relationship of 1.06 × Dc ≦ Db ≦ 1.18 × Dc is satisfied. If this ratio is less than 1.06, the tire stiffness decreases and it becomes difficult to cover the turn-down ply cylinder 14B on the turn-up ply cylinder 14A. Prone to wrinkles.

  In the method for manufacturing a radial tire for an aircraft, the driving density of the carcass cords of the turn-up ply 4A and the turn-down ply 4B is not particularly limited, but in particular 40/50 mm to 50/50 mm in a state before molding. It is desirable to set it within the range. Thereby, tire rigidity can be sufficiently secured while suppressing generation of wrinkles in the carcass layer 4.

  The tire size is 50 × 20.0R22, a bead core embedded in each of the pair of right and left bead portions, and a plurality of turns wound around each bead core and wound up from the inside of the tire to the outside. A carcass layer comprising a plurality of turn-down plies positioned outside the turn nap ply and the bead core radially inward from the turn nap ply, and a belt disposed on the outer periphery of the carcass layer in the tread portion In the production of an aircraft radial tire with a layer, only the tire molding process was varied.

Conventional Example and Comparative Examples 1 and 2:
A plurality of turn-up plies are wound around a tire molding drum to form a turn-up ply cylindrical body, and both ends of the turn-up ply are wound around a bead core, and then a plurality of layers are formed around the turn-up ply. A turn-down ply was wound to form a turn-down ply cylindrical body, and a primary green tire was formed by folding both ends of the turn-down ply into the radially inner side of the bead core. Thereafter, the carcass layer composed of the turn-up ply and the turn-down ply is expanded while the mutual interval between the bead cores is reduced, and an annular belt layer is bonded onto the outer periphery of the carcass layer, and the two including the bead core, the carcass layer, and the belt layer are included. The next green tire was molded. Thereafter, the secondary green tire was vulcanized in a mold.

Examples 1 and 2:
A turn-up ply cylinder is formed by forming a multi-layer turn-up ply into a cylindrical shape on the outer periphery of a band forming drum, and a turn-up ply is formed by forming a multi-layer turn-down ply into a cylindrical shape on the outer periphery of another band forming drum. A turn-down ply cylindrical body having an outer peripheral length equal to or less than the inner peripheral length of the cylindrical body is formed, the turn-up ply cylindrical body is disposed on the outer periphery of the tire molding drum, and both end portions of the turn-up ply are respectively Winding up around the bead core, expanding the turn-down ply cylinder and placing it on the outer periphery of the turn-up ply cylinder, and turning both ends of the turn-down ply into the radially inner side of the bead core, the primary green tire Was molded. Thereafter, the carcass layer composed of the turn-up ply and the turn-down ply is expanded while the mutual interval between the bead cores is reduced, and an annular belt layer is bonded onto the outer periphery of the carcass layer, and the two including the bead core, the carcass layer, and the belt layer are included. The next green tire was molded. Thereafter, the secondary green tire was vulcanized in a mold.

  In the conventional example, the comparative examples 1 and 2, and the examples 1 and 2, the inner peripheral length of the turn-up ply cylinder and the outer peripheral length of the turn-down ply cylinder were varied. In Table 1, other dimensions are indicated by an index with the inner peripheral length of the conventional turn-up ply cylinder as 100.

  In each of the manufacturing methods of the conventional example, comparative examples 1 and 2, and examples 1 and 2, the occurrence of wrinkles in the vicinity of the bead portion in the primary green tire was observed. Moreover, about the tire obtained by these manufacturing methods, tire rigidity and durability were evaluated by the following test method, and the results are also shown in Table 1.

Tire stiffness:
Using a water pressure tester, water pressure was applied to the inside of each tire, the water pressure was gradually increased until the tire broke, and the water pressure when the tire broke was measured. The evaluation results are shown as an index with the conventional example being 100. A larger index value means higher tire rigidity.

durability:
Each tire was assembled into a rim, the air pressure was set to 1.22 MPa, and after performing a dynamic test in accordance with FAA TSO C62d, the number and degree of failures in each part of the tire were examined, and durability was evaluated based on the results. . The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the durability.

  As shown in Table 1, the tires of Examples 1 and 2 had less wrinkles in the vicinity of the bead portion, high tire rigidity, and superior durability compared to the conventional example. On the other hand, although the tire of Comparative Example 1 has high tire rigidity, since the generation of wrinkles in the vicinity of the bead portion is large, the effect of improving durability cannot be obtained. On the other hand, in the tire of Comparative Example 2, although the generation of wrinkles in the vicinity of the bead portion was small, the tire rigidity was low, so the effect of improving durability could not be obtained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4A Turn-up ply 4B Turn-down ply 5 Bead core 6 Belt layer 6A Belt ply 11,12 Band molding drum 13 Tire molding drum 14A Turn-up ply cylinder 14B Turn-down ply cylinder Body 15 Clamp ring

Claims (4)

  A bead core embedded in each of the pair of left and right bead portions, a plurality of layers of turn-up plies that are mounted between the bead portions and wound around the bead cores from the inside to the outside of the tire, and located outside the turn-up plies A radial tire for an aircraft, comprising: a carcass layer formed of a plurality of turndown plies folded from the tire outer side radially inward of the bead core; and a belt layer disposed on an outer periphery of the carcass layer in a tread portion. In which a plurality of layers of turn-up plies are formed into a cylindrical shape to form a turn-up ply cylinder, and a plurality of layers of turn-down plies are formed into a cylindrical shape that is the same as the inner peripheral length of the turn-up ply cylinder or A turn-down ply cylinder having an outer peripheral length of less than that is formed, and the turn-up ply cylinder is It is arranged on the outer periphery of the ear forming drum, and both end portions of the turn-up ply are wound up around the bead core, the turn-down ply cylindrical body is expanded and arranged on the outer periphery of the turn-up ply cylindrical body, Both ends of the turn-down ply are folded inward in the radial direction of the bead core, and the carcass layer composed of the turn-up ply and the turn-down ply is expanded on the outer periphery of the carcass layer while reducing the mutual interval between the bead cores. A method for manufacturing a radial tire for an aircraft, comprising: bonding an annular belt layer; molding an unvulcanized tire including the bead core, the carcass layer, and the belt layer; and vulcanizing the tire in a mold.   The radial tire for an aircraft according to claim 1, wherein a ratio of an outer peripheral length of the turn-down ply cylindrical body to an inner peripheral length of the turn-up ply cylindrical body is set in a range of 0.95 to 1.0. Manufacturing method.   The radial tire for an aircraft according to claim 1 or 2, wherein a ratio of an outer peripheral length of the turndown ply cylindrical body to an inner peripheral length of the bead core is set in a range of 1.06 to 1.18. Manufacturing method.   The ratio of the inner peripheral length of the turn-up ply cylinder to the inner peripheral length of the bead core is set in a range of 1.08 to 1.12. Manufacturing method of radial tire.

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